Magnetoresistive transducer with low magnetic moment, high coercivity stabilizing magnets

ABSTRACT

A transducing head includes a first bias element, a second bias element, and a magnetoresistive sensor positioned between the first bias element and the second bias element. The first bias element and the second bias element are each formed of a permanent magnet material having a remanent magnetic moment in a range of about 200 to about 800 emu/cm 3 . In a preferred embodiment, the permanent magnet material is an alloy comprising iron, platinum, and at least one material selected from copper, silver, magnesium, lead, zinc, bismuth, and antimony.

CROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims priority from provisional U.S. patentapplication Ser. No. 60/409,887 of Eric Walter Singleton, David JamesLarson, Christopher Loren Platt, Kurt Warren Wierman, and James KentHoward, filed on Sep. 11, 2002 and entitled, “Concept and Method forMagnetoresistive Transducer with Low Moment Symmetric StabilizingMagnet.”

BACKGROUND OF THE INVENTION

[0002] The present invention relates generally to the field of magneticdata storage and retrieval systems. More particularly, the presentinvention relates to a transducing head having a magnetoresistive sensorstabilized by permanent magnet bias elements having a low magneticmoment and a high coercivity.

[0003] A transducing head of a magnetic data storage and retrievalsystem typically includes a magnetoresistive (MR) reader portion forretrieving magnetic data stored on a magnetic media. The reader istypically formed of several layers which include an MR sensor positionedbetween two insulating layers, which are in turn positioned between twoshield layers. The MR sensor may be any one of a plurality of MR-typesensors, including, but not limited to, anisotropic magnetoresistive(AMR), giant magnetoresistive (GMR), tunneling giant magnetoresistive(TMR), spin valve, and spin tunneling sensors.

[0004] When the transducing head is placed near a magnetic medium, aresistance of the MR sensor fluctuates in response to a magnetic fieldemanating from written transitions in the magnetic medium. By providinga sense current through the MR sensor, the resistance of the sensor canbe measured and used by external circuitry to decipher the informationstored on the magnetic medium.

[0005] To operate the MR sensor properly, the sensor must be stabilizedagainst the formation of edge domains because domain wall motion resultsin electrical noise that makes data recovery difficult. A common way toachieve stabilization is with a permanent magnet abutted junction designin which permanent magnet bias elements directly abut opposite sides ofthe MR sensor. Permanent magnets have a high coercive field (i.e. arehard magnets). The magnetostatic field from the permanent magnetsstabilizes the MR sensor, prevents edge domain formation, and providesproper bias.

[0006] In recent years, MR sensor widths have been decreased toaccommodate ever-increasing areal densities of magnetic media. But, witha decrease in MR sensor widths, it has been important to maintainconstant MR sensor output by increasing MR sensor sensitivity. In priorart designs, this goal has been accomplished by several methods,including decreasing a thickness of a sensing layer of the MR sensorand/or reducing a thickness of the permanent magnet bias elements and/orrecessing the permanent magnet bias elements a distance from the MRsensor (a method introduced by U.S. patent application Ser. No.10/027,051, hereby incorporated by reference) and/or shortening a lengthof the permanent magnet bias elements (a method introduced by U.S.patent application Ser. No. 10/348,386, hereby incorporated byreference).

[0007] In the case of reducing the permanent magnet thickness,process-control issues exist with creating ever-thinner permanent magnetlayers in a volume manufacturing environment. Namely, it is difficultwith thinner permanent magnets to achieve consistent thicknesses of thelayers, particularly across a wafer upon which tens of thousands of MRsensors are built. That is, the permanent magnets formed near the centerof the wafer may be thicker than the permanent magnets formed near theedge of the wafer. Also, the photolithographic processes employed informing the permanent magnet layer may result in the two permanentmagnets associated with one MR sensor having unequal thicknesses. As thethickness of the permanent magnet bias elements is decreased, thisasymmetry in thickness becomes a substantially large percentage of thetotal MR sensor thickness. For instance, an asymmetry of 50 Angstromswould result in a 50% difference in thickness across the wafer for atargeted 100 Angstroms thick permanent magnet, whereas it would be onlya 10% difference for a targeted 500 Angstroms thick permanent magnet.

[0008] In addition to permanent magnet asymmetry, error may arise in thepermanent magnet positioning with respect to a sensing layer of the MRsensor. The positioning error may result from a variety of factors,including thickness variation of deposited layers in the process offorming a MR sensor and photolithography process variations in theprocess of forming a MR sensor. The positioning error may result in aresponse variation of a MR sensor.

[0009] Thus, there is a need for a MR sensor design having increasedsensitivity without requiring a decrease in thickness of the permanentmagnets.

BRIEF SUMMARY OF THE INVENTION

[0010] A transducing head includes a first bias element, a second biaselement, and a magnetoresistive sensor positioned between the first biaselement and the second bias element. The first bias element and thesecond bias element are each formed of a permanent magnet materialhaving a remanent magnetic moment in a range of about 200 to about 800emu/cm³. In a preferred embodiment, the permanent magnet material is analloy comprising iron, platinum, and at least one material selected fromcopper, silver, magnesium, lead, zinc, bismuth, and antimony.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a cross-sectional view of a first embodiment of acurrent-in-plane transducing head in accord with the present invention.

[0012]FIG. 2 is a cross-sectional view of a second embodiment of acurrent-in-plane transducing head in accord with the present invention.

[0013]FIG. 3 is a cross-sectional view of acurrent-perpendicular-to-plane transducing head in accord with thepresent invention.

[0014]FIG. 4 is a ternary alloy phase diagram for a copper-iron-platinumalloy at 600° C. This phase diagram is taken from page 9407 of Volume 7of Handbook of Ternary Alloy Phase Diagrams, ASM International (1995).

[0015]FIGS. 5 and 6 are graphs illustrating an effect of an atomicpercentage X of copper in a (Fe₄₀Pt₆₀)_(100−X)Cu_(X) alloy, deposited asa film, on saturation magnetization M_(S) and coercivity H_(C) of thefilm, as well as coercivity H_(C) of a (Fe₄₀Pt₆₀)_(100−X)Cu_(X) alloy,deposited as a film, as related to the temperature at which the film wasannealed for four hours.

[0016]FIGS. 7 and 8 are graphs illustrating an effect of an atomicpercentage X of copper in a Fe_(50−X)Pt₅₀Cu_(X) alloy, deposited as afilm, on saturation magnetization M_(S), and remanent magnetizationM_(R) of the film, as well as coercivity H_(C) of the film at variousanneal temperatures.

[0017]FIGS. 9 and 10 are graphs illustrating the effect of an atomicpercentage X of magnesium in a (Fe₅₀Pt₅₀)_(100−X)Mg_(X) alloy, depositedas a film, on both the coercivity H_(C) of the film at various annealtemperatures and on the saturation magnetization M_(S) of the film.

[0018]FIG. 11 is a graph illustrating the effect of an atomic percentageX of silver on a (Fe₅₀Pt₅₀)_(80−X)Cu₂₀Ag_(X) alloy, deposited as a film,on the coercivity H_(C) of the film at various anneal temperatures.

[0019]FIG. 12 is a graph illustrating the effect of an atomic percentageX of nickel-oxide on a (Fe₅₀Pt₅₀)_(80−X)Cu₂₀(NiO)_(X) alloy, depositedas a film, on the coercivity H_(C) of the film at various annealtemperatures.

[0020] FIGS. 13-18 illustrate a method of forming a transducing head inaccord with the present invention.

DETAILED DESCRIPTION

[0021]FIG. 1 is a cross-sectional view of a first embodiment ofcurrent-in-plane (CIP) transducing head 100 in accord with the presentinvention. Transducing head 100 includes magnetoresistive (MR) sensor110, first and second permanent magnet (PM) bias elements 112 and 114,first and second contacts 116 and 118, top and bottom insulating layers120 and 122, and top and bottom shields 124 and 126.

[0022] MR sensor 110 is a multilayer device operable to sense magneticflux from a magnetic media. MR sensor 110 may be any one of a pluralityof MR-type sensors, including, but not limited to, AMR, GMR, TMR, spinvalve and spin tunneling sensors. At least one layer of MR sensor 110 isa sensing layer, such as a free layer of a GMR spin valve sensor, thatrequires longitudinal biasing. Moreover, for several types of MRsensors, at least one layer of MR sensor 110 is an antiferromagneticlayer that requires annealing to set a magnetization direction therein.

[0023] For illustrative purposes only, MR sensor 110 of FIG. 1 is shownas a top spin valve having sensing layer 130, spacer layer 132, pinnedlayer 134, and antiferromagnetic layer 136. Spacer layer 132 ispositioned between sensing layer 130 and pinned layer 134, and pinnedlayer 134 is positioned between antiferromagnetic layer 136 and spacerlayer 132. Sensing layer 130 and pinned layer 134 are each generallyformed of at least one layer of a ferromagnetic material, while spacerlayer 132 is formed of a nonmagnetic material. The magnetization ofsensing layer 130 rotates freely in response to external magnetic fieldemanating from a magnetic medium, while the magnetization of pinnedlayer 134 is fixed in a predetermined direction. The magnetization ofpinned layer 134 is fixed by exchange coupling antiferromagnetic layer136 with pinned layer 134. The resistance of MR sensor 110 varies as afunction of an angle that is formed between the magnetization of sensinglayer 130 and the magnetization of pinned layer 134.

[0024] First and second PM bias elements 112 and 114 abut opposite sidesof MR sensor 110 to provide longitudinal biasing to the sensing layer ofMR sensor 110. The magnetic field from PM bias elements 112 and 114stabilizes, prevents edge domain formation, and provides proper bias forthe sensing layer of MR sensor 110. In this embodiment, PM bias elements112 and 114 are each exchanged coupled to MR sensor 110. In a preferredembodiment, first PM bias element 112 has a thickness in a range ofabout one to about three times a thickness of MR sensor 110 and secondPM bias element 114 has a thickness substantially equal to the thicknessof first PM bias element 112. More specifically, PM bias elements 112and 114 each preferably have a thickness in a range of about 200Angstroms to about 1000 Angstroms.

[0025] In prior art designs, PM bias elements 112 and 114 generallywould have been formed of a high magnetic moment, high coercivity,magnetic material, such as CoCrPt, CoCr, CoCrTa, CoCrTaPt, CoPt, orCoNiCr. As detailed above in the background section, this prior artimplementation poses design problems as MR sensor widths have decreased.Specifically, the biasing field exerted by PM bias elements 112 and 114is too powerful, and over-pins the magnetization of the sensor layer ofMR sensor 110, thereby having negative effects on MR sensor sensitivity.As also detailed above, others have addressed this problem by thinningPM bias elements 112 and 114 and/or recessing PM bias elements 112 and114 a distance from MR sensor 110 and/or shortening PM bias elements 112and 114.

[0026] The present invention, however, addresses this problem byutilizing a low remanent magnetic moment, high coercivity, magneticmaterial for PM bias elements 112 and 114. The present inventionrecognizes that PM bias elements formed of a material having a lowremanent magnetic moment, specifically one having a remanent moment in arange of about 200 to about 800 emu/cm³, will exert a smallerlongitudinal biasing field upon the sensing layer of MR sensor 110 thanPM bias elements formed of a high magnetic moment material, therebyimproving the sensitivity of MR sensor 110. Another importantcharacteristic of PM bias elements 112 and 114 is a high magneticcoercivity, preferably in a range of about 2000 Oersteds (Oe) to about6000 Oe. Moreover, it is generally preferred that the material used toform PM bias elements 112 and 114 be corrosion resistant.

[0027] The remanent magnetic moment required of PM bias elements 112 and114 is dependent upon the desired stability coefficient of transducinghead 100. The stability coefficient SC is defined as:${SC} = \frac{M_{R}t_{PM}}{M_{S}t_{MR}}$

[0028] where M_(R) is the remanent magnetization of PM bias elements 112and 114, t_(PM) is the thickness of PM bias elements 112 and 114, M_(S)is the saturation magnetization of sensing layer 130, and t_(MR) is thethickness of sensing layer 130. As known by those skilled in the art,the desired magnetic moment of PM bias elements 112 and 114 is alsoaffected by a reader width of MR sensor 110, composition of sensinglayer 130, and the distance PM bias elements 112 and 114 are recessedfrom MR sensor 110, among other factors.

[0029] First and second contacts 116 and 118 are formed respectively onPM bias elements 112 and 114. Contacts 116 and 118 abut opposite sidesof MR sensor 110. Contacts 116 and 118 function to provide a sensecurrent to MR sensor 110 in a direction substantially parallel to aplane of the layers of MR sensor 110. As is generally known in theindustry, the sense current is passed through MR sensor 110 to detectchanges in the resistivity of MR sensor 110, which is indicative of thedata stored on the magnetic medium being read. Contacts 116 and 118 aretypically formed of conductive materials, such as, but not limited to,tantalum, rhodium, titanium, tungsten, chromium, copper, gold or silver.Contacts 116 and 118 are commonly formed with a thickness in a range ofabout 50 Angstroms to about 1000 Angstroms.

[0030] Top insulating layer 120 is formed adjacent MR sensor 110 andadjacent contacts 116 and 118. Bottom insulating layer 122 is formedadjacent MR sensor 110 and adjacent PM bias elements 112 and 114.Insulating layers 120 and 122 abut opposite sides of MR sensor 110.Insulating layers 120 and 122 function to magnetically decouple MRsensor 110 from shields 124 and 126. Insulating layers 120 and 122 areformed of a nonmagnetic, electrically insulating material, and arecommonly formed with a thickness in a range of about 50 Angstroms toabout 300 Angstroms.

[0031] Top shield 124 is formed on insulating layer 120 opposite MRsensor 110 and contacts 116 and 118. Bottom shield 126 is formedadjacent insulating layer 122 opposite MR sensor 110 and PM biaselements 112 and 114. Shields 124 and 126 are formed on opposite sidesof MR sensor 110. MR sensor 110 reads only that information storeddirectly beneath it on a specific track of the magnetic medium becauseshields 124 and 126 function to absorb any stray magnetic fieldsemanating from adjacent tracks and transitions.

[0032]FIG. 2 is a cross-sectional view of a second embodiment of CIPtransducing head 200 in accord with the present invention. Transducinghead 200 includes first and second PM seed layers 202 and 204, MR sensor210, first and second PM bias elements 212 and 214, first and secondcontacts 216 and 218, top and bottom insulating layers 220 and 222, andtop and bottom shields 224 and 226.

[0033] Transducing head 200 is similar to transducing head 100 of FIG.1, with the exception that transducing head 200 includes first andsecond seed layers 202 and 204. For that reason, elements common to bothFIGS. 1 and 2 are like-numbered in the last two digits, for example CIPtransducing head 100 and CIP transducing head 200. Moreover, thediscussion pertaining to those elements common to both FIGS. 1 and 2with reference to FIG. 1 applies equally to their inclusion in FIG. 2,and thus, will not be repeated below.

[0034] First and second PM seed layers 202 and 204 are deposited uponportions of bottom gap 222 not covered by MR sensor 210 and on oppositesides of MR sensor 210. PM seed layers 202 and 204 help to promote adesired texture and to enhance a desired grain growth of PM biaselements 212 and 214 grown thereon. Moreover, PM seed layers 202 and 204function to magnetically decouple PM bias elements 212 and 214 from MRsensor 210. In this embodiment, PM bias elements 112 and 114 are eachmagnetostatically coupled to MR sensor 210. In a preferred embodiment,PM seed layers 202 and 204 each have a thickness less than about 100Angstroms.

[0035]FIG. 3 is a cross-sectional view of current-perpendicular-to-plane(CPP) transducing head 300 in accord with the present invention.Transducing head 300 includes tunneling giant magnetoresistive (TMR)sensor 310, PM bias elements 312 and 314, insulating layers 316, 318,320, and 322, and top and bottom shields 324 and 326. CPP transducinghead 300 differs from CIP transducing heads 100 and 200 in that thesense current provided to TMR sensor 310 is provided in a directionsubstantially perpendicular to the planes of layers (not shown) of TMRsensor 310, rather than in a direction substantially parallel.

[0036] TMR sensor 310 is a multilayer device operable to sense magneticflux from a magnetic media. At least one layer of TMR sensor 310 is asensing layer that requires longitudinal biasing. Moreover, TMR sensor310 may include an antiferromagnetic layer that requires annealing toset a magnetization direction therein.

[0037] First and second PM bias elements 312 and 314 are positioned onopposite sides of TMR sensor 310 to provide longitudinal biasing to thesensing layer of TMR sensor 310. PM bias elements 312 and 314 arerecessed from TMR sensor 310 a distance in a range of about 20 Angstromsto about 300 Angstroms. Thus, PM bias elements 312 and 314 aremagnetostatically coupled with TMR sensor 310. PM bias elements 312 and314 are otherwise similar to PM bias elements 112 and 114 of FIG. 1 andPM bias elements 212 and 214 of FIG. 2.

[0038] Insulating layer 316 is positioned between bottom shield 326 andfirst PM bias element 312, and also between first PM bias element 312and TMR sensor 310. Similarly, insulating layer 318 is positionedbetween bottom shield 326 and second PM bias element 314, and is alsopositioned between second PM bias element 314 and TMR sensor 310.Insulating layers 320 and 322 are positioned on a respective one of PMbias elements 312 and 314 on opposing sides of TMR sensor 310.Insulating layers 316, 318, 320, and 322 function to magneticallydecouple TMR sensor 310 from shields 324 and 326. Insulating layers 316,318, 320, and 322 also preferably function to minimize the shunting ofsense current from TMR sensor 310 to PM bias elements 312 and 314. Eachof insulating layers 316, 318, 320, and 322 is formed of nonmagneticmaterial, and are commonly formed with a thickness in a range of about50 Angstroms to about 300 Angstroms.

[0039] Top shield 324 is formed adjacent to TMR sensor 310 andinsulating layers 320 and 322. Bottom shield 326 is formed adjacent toTMR sensor 310 and insulating layers 316 and 318. Shields 324 and 326are formed on opposite sides of TMR sensor 310. TMR sensor 310 readsonly information stored directly beneath it on a specific track of amagnetic medium because shields 324 and 326 function to absorb any straymagnetic fields emanating from adjacent tracks and transitions. Inaddition, shields 324 and 326 function to provide a sense current to TMRsensor 310 in a direction substantially perpendicular to planes oflayers (not shown) of TMR sensor 310. Sense current is passed throughTMR sensor 310 to detect changes in the resistivity of TMR sensor 310,which are indicative of the data stored on the magnetic medium beingread. Shields 324 and 326 preferably are composed of a soft magneticmaterial, such as, but not limited to, an NiFe alloy. Shields 324 and326 are commonly formed with a thickness in a range of about one-tenthmicron to about ten microns.

[0040] While the present invention contemplates the use of any lowmagnetic moment, high coercivity, corrosion resistant permanent magneticmaterial, one material found to perform well is an alloy formed of atleast iron, platinum, and A, where A may be copper, gold, silver,magnesium, lead, zinc, bismuth, antimony, or another suitable material.A may also be an alloy of copper and at least one of gold, silver,magnesium, nickel-oxide, lead, zinc bismuth, antimony, or anothersuitable material. This alloy can be represented as:

(Fe_(100−Y)Pt_(Y))_(100−Z)A_(Z)

[0041] where Y represents an atomic percentage of platinum in the alloyrelative to an atomic percentage of iron, and Z represents the atomicpercentage of element A in the alloy. A preferred range for Y is between35 and 65 atomic percent and for Z is between 0 and 60 atomic percent. Amore preferred range for Y is between 40 and 60 atomic percent and for Zis between 15 and 40 atomic percent.

[0042] A most preferred permanent magnet material isiron-platinum-copper. FIG. 4 is a ternary alloy phase diagram for acopper-iron-platinum alloy at 600° C. This phase diagram is taken frompage 9407 of Volume 7 of Handbook of Ternary Alloy Phase Diagrams, ASMInternational (1995). Region 400 of the phase diagram represents thosecombinations of copper, iron, and platinum having a composition close tothe L1₀Fe₅₀Pt₅₀ phase, a low magnetic moment and which retain thedesired one-phase micro-structure (desired for good for magneticproperties). In FIG. 4, line 402 identifies Fe₅₀Pt₅₀, while line 404identifies a percentage of copper at point 402, defined as theintersection of line 402 with region 400. More specifically, point 402identifies a combination of copper, iron, and platinum having about 78%Fe₅₀Pt₅₀ and 22% copper.

[0043] For alloys of iron, platinum, and copper annealed at lowertemperatures, the boundaries of region 400 will move. Thus, a desiredrange of atomic percentages of copper in the alloy is about 16 to about40.

[0044] The ability to substitute a large amount of A in this alloyallows for a potentially large reduction of magnetic moment compared topure iron-platinum in the L1₀ phase. However, the addition of a large ofamount of A into the (Fe_(100−Y)Pt_(Y))_(100−Z)A_(Z) alloy may modifythe L1₀ ordering kinetics. To function as biasing elements, PM biaselements 112 and 114 formed of the (Fe_(100−Y)Pt_(Y))_(100−Z)Cu_(Z)alloy must be annealed to transform the (Fe_(100−Y)Pt_(Y))_(100−Z)Cu_(Z)alloy into the L1₀ crystalline phase. Since several elements of thetransducing head generally cannot withstand annealing temperatures inexcess of 300° C., an advantage of the (Fe_(100−Y)Pt_(Y))_(100−Z)Cu_(Z)alloy is that Cu does not aid growth of the L1₀ phase at lowtemperatures, more specifically, at temperatures less than 350° C.

[0045]FIG. 5 is a graph illustrating an effect of an atomic percentage Xof copper in a (Fe₄₀Pt₆₀)_(100−X)Cu_(X) alloy, deposited as a film, onsaturation magnetization M_(S) (which is indicative of magnetic moment)and coercivity H_(C) of the film. The film illustrated in FIG. 5 wasdeposited to 1000 Angstroms thick, and was annealed at 300° C. for fourhours. Line 500 of FIG. 5 illustrates the effect of copper in the filmon coercivity H_(C) of the unannealed film, while line 502 illustratesthe effect on the annealed film. Similarly, line 504 illustrates theeffect of copper on the saturation magnetization M_(S) of the unannealedfilm, while line 506 illustrates the effect on the annealed film. Forreference, the saturation magnetization M_(S) of common prior artpermanent magnets is about 800 emu/cc and the saturation magnetizationM_(S) of un-doped iron-platinum is about 1000 emu/cc. By substantiallyreducing the magnetic moment of the PM bias elements to about 400emu/cc, one may design a transducing head having PM bias elementssufficiently thick to greatly reduce the position variation and magnetasymmetry associated with ever-thinner prior art PM bias elements.

[0046] An additional advantage associated with the selection of lowmagnetic moment alloys of iron, platinum, and copper includes the factthat the copper composition can be varied over some range to allow thedesigner to tune the remanent magnetic moment in conjunction with adesired thickness of the PM bias elements to provide a desired stabilitycoefficient to stabilize the sensing layer of the MR sensor.

[0047] Moreover, the (Fe₄₀Pt₆₀)_(100−X)Cu_(X) alloy does not require aseed layer, thus allowing for greater flexibility in the design oftransducing heads in accord with the present invention. Accordingly, thedesigner may choose to use a buffer layer or seed layer beneath the PMbias elements of only tens of Angstroms thick to hundreds of Angstromsthick to magnetically decouple the PM bias elements from the sensinglayer of the MR sensor. Or, the designer may choose to use no buffer orseed layer, thereby ferromagnetically coupling the PM bias elements tothe sensing layer of the MR sensor. The magnetic materials traditionallyused for forming PM bias elements require a seed layer to develop asufficiently high magnetic coercivity.

[0048] Another advantage of the (Fe₄₀Pt₆₀)_(100−Y)Cu_(X) alloy is itsrelatively low ordering temperature. To obtain the magnetically hard L1₀phase, the (Fe₄₀Pt₆₀)_(100−X)Cu_(X) PM bias elements must be annealed.Because of the low anneal temperature, the PM bias elements may beannealed simultaneously with the annealing of an antiferromagnetic layerthat may be included in the MR sensor required to set an anisotropydirection of the antiferromagnetic layer. FIG. 6 is a graph illustratingcoercivity H_(C) of the (Fe₄₀Pt₆₀)_(100−X)Cu_(X) alloy, deposited as afilm 800 Angstroms thick, as related to the temperature at which thefilm was annealed for four hours. As shown in FIG. 6, coercivity H_(C)of the film increases substantially with an anneal of at least 280° C.,and is preferably at least 300° C. for use in conjunction withtransducing heads. One advantage of simultaneously annealing the PM biaselements and an antiferromagnetic layer of the MR sensor is that a largeshape anisotropy resulting from a definition of a reader width of the MRsensor helps to define the anisotropy direction of the antiferromagneticlayer.

[0049] The (Fe₄₀Pt₆₀)_(100−X)Cu_(X) alloy is additionally advantageousin that it offers superior resistance to demagnetization. It has a highcoercive field of about 4000 Oe to about 7000 Oe, in comparison to the2000 Oe to 2500 Oe of conventional CoCr or CoCrX alloys of prior art PMbias element designs.

[0050] Moreover, the (Fe₄₀Pt₆₀)_(100−X)Cu_(X) alloy has a sufficientlyhigh Curie temperature which offers good thermal stability and offersacceptable resistance to corrosion resistance, making this materialcompatible with existing transducing head processes.

[0051] FIGS. 7-12 illustrate the suitability of several other alloys informing PM bias elements. FIG. 7 is a graph illustrating an effect of anatomic percentage X of copper in a Fe_(50−X)Pt₅₀Cu_(X) alloy, depositedas a film, where the atomic percent of Pt is set at 50, on saturationmagnetization M_(S) and remanent magnetization M_(R) of the film. Thealloy illustrated in FIG. 7 was deposited as a film 500 Angstroms thickand annealed at 650° C. for ten minutes. As the atomic percentage X ofcopper in the film increases, the saturation magnetization Ms andremanent magnetization M_(R) of the film decrease.

[0052]FIG. 8 is a graph illustrating the effect of an atomic percentageX of copper in a Fe_(50−X)Pt₅₀Cu_(X) alloy, deposited as a film, oncoercivity H_(C) of the film at various anneal temperatures. The alloysillustrated in FIG. 8 were each deposited as a film 500 Angstroms thickand annealed at 650° C. for ten minutes. Line 510 of FIG. 8 represents aFe₅₀Pt₅₀ film, while line 512 represents a Fe₄₄Pt₅₀Cu6 film, line 514represents a Fe₃₉Pt₅₀Cu₁₁ film, and line 516 represents a Fe₃₃Pt₅₀Cu₁₇film. For a given anneal temperature, coercivity H_(C) of the filmdecreases as an atomic percentage X of copper increases in the FePtCufilm.

[0053]FIG. 9 is a graph illustrating the effect of an atomic percentageX of magnesium in a (Fe₅₀Pt₅₀)_(100−X)Mg_(X) alloy, deposited as a film,on coercivity H_(C) of the film at various anneal temperatures. Thealloys illustrated in FIG. 9 were each deposited as a film 500 Angstromsthick, and were rapid thermal process (RTP) annealed for ten minutes atvarious temperatures. Line 520 of FIG. 9 represents a Fe₅₀Pt₅₀ film,while line 522 represents a (Fe₅₀Pt₅₀)₉₀Mg₁₀ film, line 524 represents a(Fe₅₀Pt₅₀)₈₀Mg₂₀film, and line 516 represents a (Fe₅₀Pt₅₀)₆₀Mg₄₀ film.For a given anneal temperature, coercivity HC of the film decreases asthe atomic percentage X of magnesium increases in the FePtMg film.

[0054]FIG. 10 is a graph illustrating the effect of an atomic percentageX of magnesium in a (Fe₅₀Pt₅₀)_(100−X)Mg_(X) alloy, deposited as a film,on saturation magnetization M_(S) of the film. The alloys illustrated inFIG. 10 were each deposited as a film 500 Angstroms thick. As shown inFIG. 10, as the atomic percentage X of magnesium in the film increases,the saturation magnetization M_(S) of the film decreases.

[0055]FIG. 11 is a graph illustrating the effect of an atomic percentageX of silver on a (Fe₅₀Pt₅₀)_(80−X)Cu₂₀Ag_(X) alloy, deposited as a film,on the coercivity H_(C) of the film at various anneal temperatures. Thealloys illustrated in FIG. 11 were each deposited as a film 200Angstroms thick on a 50 Angstrom thick MgO seedlayer and were RTPannealed for 10 minutes. Line 530 of FIG. 11 represents a(Fe₅₀Pt₅₀)₈₀Cu₂₀film, while line 532 represents a (Fe₅₀Pt₅₀)₇₀Cu₂₀Ag₁₀film, line 534 represents a (Fe₅₀Pt₅₀)₆₀Cu₂₀Ag₂₀ film, line 536represents a (Fe₅₀Pt₅₀)₅₀Cu₂₀Ag₃₀ film, and line 538 represents a(Fe₅₀Pt₅₀)₄₀Cu₂₀Ag₄₀ film. At 350° C., as the atomic percentage X ofsilver increases in the FePtCuAg film, the coercivity H_(C) decreases.Similarly at higher anneal temperatures, the coercivity of the FePtCuAgfilm generally decreases as the atomic percentage of silver isincreased. It is noted that the (Fe₅₀Pt₅₀)₈₀Cu₂₀ film, at higher annealtemperatures, breaks this trend and has a lower coercivity H_(C) thanthe films having greater percentages of silver.

[0056]FIG. 12 is a graph illustrating the effect of an atomic percentageX of nickel-oxide on a (Fe₅₀Pt₅₀)_(80−X)Cu₂₀(NiO)_(X) alloy, depositedas a film, on the coercivity H_(C) of the alloy at various annealtemperatures. The alloys illustrated in FIG. 12 were each deposited as afilm 200 Angstroms thick on a 50 Angstrom thick MgO seedlayer and wereRTP annealed for 10 minutes. Line 540 of FIG. 12 represents a(Fe₅₀Pt₅₀)₇₀Cu₂₀(NiO)₁₀ film, line 542 represents a(Fe₅₀Pt₅₀)₆₀Cu₂₀(NiO)₂₀ film, and line 544 represents a(Fe₅₀Pt₅₀)₅₀Cu₂₀(NiO)₃₀ film. At a given anneal temperature, an increasein the atomic percentage X of NiO in the FePtCuNiO film results in adecrease in the coercivity H_(C). Also illustrated in FIG. 12 is line546 representing a (Fe₅₀Pt₅₀)₈₀(NiO)₂₀ film.

[0057] Experimental data, literature, and ternary phase diagrams confirmthat an iron-platinum alloy doped with at least one of gold, silver ormagnesium will yield similar results as the (Fe₄₀Pt₆₀)_(100−X)Cu_(X)alloy described above. Furthermore, the properties of lead, zinc,bismuth, and antimony indicate that an iron-platinum alloy doped with atleast one of these elements will also yield results similar to the(Fe₄₀Pt₆₀)_(100−X)Cu_(X) alloy described above.

[0058] FIGS. 13-18 illustrate a method of forming a transducing head inaccord with the present invention. FIG. 13 shows a first step, in whicha plurality of MR sensor layers 700 are deposited on a substrate (notshown). FIG. 14 shows a following step in which a portion of MR sensorlayers 700 is masked off by photoresist 712, wherein photoresist 712defines MR sensor width W_(MR). FIG. 15 shows the next step, in whichstructure 714 is milled, removing portions of MR sensor layers 700 thatare not masked off. The result is MR sensor 716 with a MR sensor widthW_(MR). In FIG. 16, PM bias element material 718 is deposited,specifically, adjacent MR sensor 716 and on top of photoresist 712. FIG.17 shows the next step, in which contact material 720 is deposited on PMbias element material 718. FIG. 18 shows the structure of FIG. 17 afterphotoresist 712, along with PM bias element material 718 and contactmaterial 720 deposited thereon, are removed using conventionaltechniques. The structure of FIG. 18 is then annealed at a suitabletemperature for a suitable time to cause a substantial amount of PM biaselement material 718 to structurally transform to the L1₀ phase. To theextent that one of the plurality of layers of MR sensor 716 is anantiferromagnetic layer needing to be annealed, the annealing of PM biaselement material 718 preferably occurs in the presence of a magneticfield in a desired direction of the magnetization of theantiferromagnetic layer.

[0059] In summary, by using a low remanent magnetic moment, highcoercivity, corrosion resistant material in forming PM bias elements ofa transducing head, the present invention is a solution for the positionand asymmetry error associated with prior art designs associated withnarrow read width transducing heads.

[0060] Although the present invention has been described with referenceto preferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

1. A transducing head comprising: a magnetoresistive sensor; a firstbias element; and a second bias element, wherein the magnetoresistivesensor is positioned between the first bias element and the second biaselement, and wherein the first bias element and the second bias elementare each formed of a permanent magnet material having a remanentmagnetic moment in a range of about 200 emu/cm³ to about 800 emu/cm³. 2.The transducing head of claim 1, wherein the permanent magnet materialhas a coercivity in a range of about 2000 Oersteds to about 6000Oersteds.
 3. The transducing head of claim 1, wherein the permanentmagnet material is in an iron-platinum L1₀ phase having an orderingtemperature less than about 600° C.
 4. The transducing head of claim 1,wherein the permanent magnet material is an alloy comprising iron,platinum, and copper.
 5. The transducing head of claim 1, wherein thepermanent magnet material is an alloy comprising iron, platinum, and atleast one element selected from a group consisting of copper, magnesium,gold, silver, lead, zinc, bismuth, and antimony.
 6. The transducing headof claim 5, wherein an atomic percentage of the at least one element inthe alloy is in a range of 0 to about
 60. 7. The transducing head ofclaim 5, wherein an atomic percentage of the at least one element in thealloy is in a range of about 15 to about
 40. 8. The transducing head ofclaim 1, wherein the permanent magnet material is a first alloycomprising iron, platinum, and a second alloy, the second alloycomprising copper and at least one element selected from a groupconsisting of magnesium, gold, silver, nickel-oxide, lead, zinc,bismuth, and antimony.
 9. The transducing head of claim 8, wherein anatomic percentage of the second alloy in the first alloy is in a rangeof 0 to about
 60. 10. The transducing head of claim 8, wherein an atomicpercentage of the second alloy in the first alloy is in a range of about15 to about
 40. 11. The transducing head of claim 1, wherein the firstbias element has a thickness in a range of about one to about threetimes a thickness of the magnetoresistive sensor and the second biaselement has a thickness substantially equal to the thickness of thefirst bias element.
 12. The transducing head of claim 1 and furthercomprising: a first seed layer upon which the first bias element isformed, wherein a thickness of the first seed layer is less than about100 Angstroms; and a second seed layer upon which the second biaselement is formed, wherein a thickness of the second seed layer issubstantially equal to the thickness of the first seed layer.
 13. Thetransducing head of claim 12 wherein the first seed layer magneticallydecouples the first bias element from the magnetoresistive sensor andthe second seed layer magnetically decouples the second bias elementfrom the magnetoresistive sensor.
 14. A transducing head comprising: amagnetoresistive sensor; a first bias element; and a second biaselement, wherein the magnetoresistive sensor is positioned between thefirst bias element and the second bias element, and wherein the firstbias element and the second bias element are each formed of an alloycomprising iron, platinum, and at least one element selected from agroup consisting of copper, magnesium, gold, silver, lead, zinc,bismuth, and antimony, and wherein an atomic percentage of the elementin the alloy is in a range of about 15 to about
 40. 15. The transducinghead of claim 14, wherein the at least one element is copper.
 16. Thetransducing head of claim 14, wherein the alloy is in an iron-platinumL1₀ phase having an ordering temperature less than about 600° C.
 17. Thetransducing head of claim 14, wherein the alloy has a remanent magneticmoment in a range of about 200 emu/cm³ to about 800 emu/cm³.
 18. Thetransducing head of claim 14, wherein the alloy has a coercivity in arange of about 2000 Oersteds to about 6000 Oersteds.
 19. The transducinghead of claim 14, wherein the first bias element has a thickness in arange of about one to about three times a thickness of themagnetoresistive sensor and the second bias element has a thicknesssubstantially equal to the thickness of the first bias element.
 20. Thetransducing head of claim 14 and further comprising: a first seed layerupon which the first bias element is formed, wherein a thickness of thefirst seed layer is less than about 100 Angstroms; and a second seedlayer upon which the second bias element is formed, wherein a thicknessof the second seed layer is substantially equal to the thickness of thefirst seed layer.
 21. The transducing head of claim 19, wherein thefirst seed layer magnetically decouples the first bias element from themagnetoresistive sensor and the second seed layer magnetically decouplesthe second bias element from the magnetoresistive sensor.
 22. A methodfor forming a transducing head comprising: depositing and defining asensor width of a magnetoresistive sensor, the magnetoresistive sensorcomprising an antiferromagnetic layer depositing first and second biaselements adjacent opposite ends of the magnetoresistive sensor, whereinthe first and second bias elements are each formed of a permanent magnetmaterial having a remanent magnetic moment in the range of about 200emu/cm³ to about 800 emu/cm³; annealing the transducing head at atemperature in a range of about 280° C. to about 600° C. in the presenceof a magnetic field to set a magnetization of the anti ferromagneticlayer of the magnetoresistive sensor and to transform the permanentmagnet material into an iron-platinum L1₀ phase.
 23. The method of claim22, wherein the permanent magnet material has a coercivity in a range ofabout 2000 Oersteds to about 6000 Oersteds.
 24. The method of claim 22,wherein the permanent magnet material is an alloy comprising iron,platinum, and copper.
 25. The method of claim 22, wherein the permanentmagnet material is an alloy comprising iron, platinum, and at least oneelement selected from a group consisting of copper, magnesium, gold,silver, lead, zinc, bismuth, and antimony.
 26. The method of claim 25,wherein an atomic percentage of the element in the alloy is in a rangeof 0 to about
 60. 27. The method of claim 25, wherein an atomicpercentage of the element in the alloy is in a range of about 15 toabout
 40. 28. The method of claim 22, wherein the permanent magnetmaterial is a first alloy comprising iron, platinum, and a second alloy,the second alloy comprising copper and an element selected from a groupconsisting of magnesium, gold, silver, nickel-oxide, lead, zinc,bismuth, and antimony.
 29. The method of claim 28, wherein an atomicpercentage of the second alloy in the first alloy is in a range of about0 to about
 60. 30. The method of claim 28, wherein an atomic percentageof the second alloy in the first alloy is in a range of about 15 toabout
 40. 31. The method of claim 22, wherein the first bias element hasa thickness in a range of about one to about three times a thickness ofthe magnetoresistive sensor and the second bias element has a thicknesssubstantially equal to the thickness of the first bias element.